MR MICROSCOPY OF ENDOLYMPHATIC HYDROPS

Duke University, Durham NC

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Abstract

In 1991, anesthesiologists reported six new cases of persistent neurologic deficits after continuous spinal anesthesia in patients using hyperbaric 5% lidocaine . The neurological symptoms consisted mainly of saddle anesthesia and sphincter dysfunction. Although computed tomography, magnetic resonance imaging and electromyography were diagnostically inconclusive it was referred to as a lidocaine-induced "cauda equina syndrome". The pathophysiological mechanisms underlying the neurologic complications were not clear but were thought to be related to (a) use of higher than normal doses of hyperbaric 5% lidocaine and (b) spinal microcatheters directed sacrally. As a consequence of these studies, the FDA withdrew manufacturers' marketing approvals for small-bore catheters (under 27 G) for intrathecal use. Recently, symptoms suggestive of transient radicular irritation were observed in patients after "single shot" spinal anesthesia with 5% and 2% lidocaine. Today patients are increasingly exposed to local anesthetics when peripheral or central nervous blockade is used during surgery or post-operatively for analgesia. To avoid future complications, it is important to determine the etiology of local anesthetic-induced neurotoxicity and to determine how to control its occurrence. In this proposal, we use diffusion-weighted magnetic resonance microscopy to characterize lidocaine-induced spinal cord damage. The proposed studies should provide new insights into how diffusion-weighted magnetic resonance imaging can be used to diagnose early lidocaine-induced neurotoxicity. It is our long-term goal that data derived from this research will be applicable to future clinical as well as experimental studies with new intrathecal drugs for anesthesia and/or analgesia.